An ink jet recording method is a recording method involving applying a small ink droplet to any one of recording media such as plain paper and glossy media to form an image, and had become rapidly widespread owing to a reduction in its cost and an improvement in its recording rate. With the rapid spread of a digital camera in addition to an improvement in quality of an image recorded by the method, the method has been generally used as a method of outputting a photographic image comparable to a silver halide photograph. Based on this, performance required to an ink jet recording method of an outputting method has been diversified. As for the picture quality, for instance, high color developability and a wide color-reproducing range have been required, so as to faithfully reproduce the image sent from an outputting source, as the digital camera acquires higher resolution and higher sensitivity.
On the other hand, a problem is pointed out that the quality of an image in an obtained recorded matter by an ink jet recording method is not kept so long as that in a silver halide photograph. There has been a problem that an image quality in a recorded matter obtained by the ink jet recording method is kept not longer than that in the silver halide photograph in general, and that the image tends to cause the change of its color tone and color fading due to the deterioration of a coloring material, when the recorded matter is exposed to light, humidity, heat and a environmental gas existing in the air for a long period of time. It has been a conventional problem for the ink jet recording system to improve particularly the environmental gas resistance up to a level of the silver halide photograph. Cyan has the lowest environmental gas resistance among yellow, magenta, and cyan, which are hues used for ink. Therefore, it has been one of the important problems in the ink jet recording method to improve the environmental gas resistance of the cyan ink to the level comparable to that of yellow ink or magenta ink.
The basic skeletons of coloring materials for ink having a cyan hue are roughly classified into a phthalocyanine skeleton and a triphenylmethane skeleton. The representative coloring materials of the former include C.I. Direct Blue 86 and 87, and C.I. Direct Blue 199. Representative coloring materials of the latter include C.I. Acid Blue 9.
In general, a phthalocyanine-based coloring material is characterized in that it is excellent in alight resistance as compared to a triphenylmethane-based coloring material. Furthermore, the phthalocyanine-based coloring material has high fastness properties against humidity or heat and has good color developability, and so the coloring material has been vigorously used as a coloring material for ink.
However, the phthalocyanine-based coloring material tends to be inferior in fastness against environmental gases in the air (such as ozone, NOx or SO2), especially an ozone gas. In particular, in a recorded product obtained by applying the coloring material on a recording medium having an ink-receiving layer containing an inorganic substance such as alumina or silica, the fastness of a recorded matter is remarkably low, so the color fading of the recorded matter is remarkable when the recorded product is left standing in a room for a long period of time. For the purpose of improving the environmental gas resistance, various dyes have been proposed which are represented by the dye disclosed in Japanese Patent Application Laid-Open No. 2004-323605, for instance.
In addition, Japanese Patent Application Laid-Open No. 2002-105349 discloses that an ink containing a mixture of cyan dyes formed of copper phthalocyanine having a —SO2NH2 group and a —SO2M group as a substituent group provides a recorded matter which causes a little change in color even when having been left unattended in ozone gas. Japanese Patent Laid-Open No. 2002-105349 also discloses that the cyan dye mixture with a little change in the color among such cyan dye mixtures is specified by two methods described below. The first judgment method will be now described below. In an absorption curve obtained when the cyan dye mixture is dissolved in N,N-dimethyl formaldehyde and the absorbance is measured with a spectrophotometer while adjusting an absorbance to 1 to 2 Abs, an absorption peak wavelength in a range of 615 to 640 nm shall be defined as C, and an absorption peak wavelength in a range of 655 to 680 nm shall be defined as D. Then, the cyan dye mixture with little change in the color should have a value (D−C) of 48 nm or less. The second judgment method will be now described below. In a chromatogram obtained when the cyan dye mixture is dissolved in an aqueous solution of acetonitrile/ammonium dihydrogen phosphate of a developing solvent and the chromatogram is measured with a high-performance liquid chromatography, an absorption peak wavelength in a range of 590 to 630 nm shall be defined as A, and an absorption peak wavelength in a range of 640 to 670 nm shall be defined as B. Then, the cyan dye mixture with a little change in the color contains only a component showing a value B/A of 1 or less.
The phthalocyanine-based coloring material involves another problem, that is, the occurrence of a metallic luster resulting from a high aggregation property of the coloring material, referred to as a bronze phenomenon. When the bronze phenomenon occurs in a recorded matter, the optical reflectance property of the recorded matter changes. As a result, the color developability and hue of an image remarkably change, with the result that a remarkable reduction in image quality occurs. The bronze phenomenon is considered to occur as a result of the aggregation of the coloring material on the surface of a recording medium due to, for example, the high aggregation properties of the coloring material in ink and a reduction in permeability of the ink into the recording medium when the ink is applied to the recording medium. In particular, a coloring material having introduced in a molecule thereof an amino group for the purpose of improving environmental gas resistance, or ink containing a coloring material having low solubility in water tends to cause a remarkable bronze phenomenon.
For instance, Japanese Patent No. 2942319 proposes a specific phthalocyanine-based coloring material is used to improve environmental gas resistance. The use of the specific phthalocyanine-based coloring material provides environmental gas resistance which is one of concern in the phthalocyanine-based coloring material.